1. Field of the Invention
The invention relates to an apparatus for maintaining a positioning force on movable parts within a guide means. In the apparatus of the present invention there is provided a pressure roller with a cylindrical rolling surface and a leaf spring for generating a compression force which mounts the pressure roller at a part to be guided, such as a scanning carriage of a measuring system. The measuring system may be a known incremental path measuring system, wherein the scanning carriage must be guided very precisely to avoid measuring errors.
2. Description of the Prior Art
In the prior art positioning apparatus such as disclosed in German Gebrauchsmuster No. 7,507,398 are provided in measuring systems in which a measuring rod and a scanning carriage are mounted in a rigid hollow body for protection from environmental influences. The scanning carriage is seated directly at the scale by way of sliding shoes and at the hollow body via ball bearings. With the aid of a pressure roller which is a ball bearing seated at the hollow body on a planar surface, the scanning carriage is urged against the guiding surfaces of the measuring rod and the hollow body. A leaf spring is provided to generate the positioning force, to mount the pressure roller, and to fasten the pressure roller to the scanning carriage. The hollow body is sealed to provide protection against environmental influences by means of flexible sealing lips arranged in a roof-like manner upon a connecting means for attaching the scanning carriage to a mounting.
The prior art apparatus has the disadvantage of a mounting for the pressure roller which does not allow angular movement of the pressure roller, such as adjustments in the axis of rotation of the pressure roller, in order to compensate for unevenness in the guiding surfaces and minor deviations from the desired parallel relationship of the axis of rotation and the guiding surface. Without allowance for adjustment, forces may act on the scanning carriage which could possibly result in adulteration of a reading taken by the measuring system.